/Engine/Plugins/Experimental/Mutable/Source/MutableTools/Public/MuT/NodeModifierMeshClipMorphPlane.h
Define an axis-aligned box that will select the vertices to be morphed. Only one of Box or Bone Hierarchy can be used (the last one set)
void SetVertexSelectionBox ( float centerX, float centerY, float centerZ, float radiusX, float radiusY, float radiusZ )